Mackay had been in critical condition at a California hospital with the life-threatening infection, which can lead to multiple organ failure. Family members were said to have gathered at the intensive-care unit at Seton Medical Center in Daly City.

"Steve was a classic '60s American guy, full of generosity and love for anyone he met," Stooges frontman Iggy Pop said in a statement. "Every time he put his sax to his lips and honked, he lightened my road and brightened the whole world. He was a credit to his group and his generation. To know him was to love him."

Later a sideman with the Violent Femmes, Mackay rose to fame for his work on the Stooges' 1970 album Fun House. Pop is now the only surviving member of that classic lineup. Stooges bassist Dave Alexander died in 1975, followed by guitarist Ron Asheton in 2009, and Asheton's drum-playing brother Scott in 2014.

Their 1970 album together was later expanded into a gigantic, seven-disc box set in 1999 titled The Complete Fun House Sessions. Mackay then returned to perform on the Stooges' comeback albums, 2007's Ready to Die and 2013's The Weirdness – the latter of which followed the group's induction into the Rock and Roll Hall of Fame in 2010.

Over the years, Mackay also collaborated with Commander Cody and a string of bands in the Bay Area, where he had lived since the mid-'70s.